Empirical Assessment and Reusability of an Eco-Friendly Amine-Functionalized SBA-15 Adsorbent for Aqueous Ivermectin

• Published in: Industrial & engineering chemistry research Vol. 60; no. 6; pp. 2365 - 2373
• Main Authors: Diagboya, Paul N, Mtunzi, Fanyana M, Düring, Rolf-Alexander, Olu-Owolabi, Bamidele I
• Format: Journal Article
• Language: English
• Published: American Chemical Society 17-02-2021
• Subjects: Applied Chemistry
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.0c05115

Ivermectin has efficacious broad-spectrum action against several human and veterinary endo-/ectoparasites. However, it is an emerging contaminant in water, causing serious concern to environmental health experts because of its toxicity/adverse ecological effects and increasing input. Currently, conventional water treatment methods are not designed to effectively eliminate it. Hence, amine moiety-grafted SBA-15 (SBA-15-NH2) was prepared, characterized, and evaluated for ivermectin adsorption from water as well as its reusability. Ivermectin adsorption data were analyzed with pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models, in addition to Langmuir and Freundlich adsorption isotherm models and the thermodynamics parameters evaluated. Characterization data revealed that the SBA-15 mesoporous structure was intact in SBA-15–NH2 with reduced surface areas and pore sizes. The SBA–15 characteristic hydroxyl group infrared broad band disappeared with the appearance of stronger amide–I band upon functionalization. In addition, SBA–15-NH2 has ≈22% less thermal stability than the SBA–15, while both materials exhibited intense X-ray diffraction peaks typical of well-organized pore structures with no significant distortion after functionalization. Ivermectin adsorption was rapid, and equilibrium was reached within 180 min. The pseudo-second order kinetic model fit the data better than the pseudo-first order one, suggesting electrostatic interaction as a removal mechanism, while the intraparticle diffusion model indicated that ≈80% ivermectin uptake occurred on the external surfaces. The process was pH- and concentration-dependent and exhibited higher adsorption at extreme pH conditions (pH values ≈3 and 11) and higher concentrations. The SBA–15-NH2 adsorption capacity is 536.2 μg/g at 30 °C, while the concentration left in solution could be as low as 1 μg/L. Adsorption isotherm models revealed that the process involves multiple reaction phenomena including monolayer, heterogeneous, and multilayer adsorption simultaneously. Adsorption was spontaneous but exothermic, and thus, it decreased at high ambient temperature. The SBA-15-NH2 adsorbent exhibited potential for reusability with about 15% loss in efficiency after 3 cycles of adsorption and desorption.